CN110957431A

CN110957431A - Platinum complex-based organic light-emitting device suitable for wet preparation

Info

Publication number: CN110957431A
Application number: CN201911207382.4A
Authority: CN
Inventors: 程刚; 毛茂; 支志明
Original assignee: Shenzhen Institute of Research and Innovation HKU
Current assignee: Shenzhen Institute of Research and Innovation HKU
Priority date: 2019-11-29
Filing date: 2019-11-29
Publication date: 2020-04-03

Abstract

The invention discloses a platinum complex-based organic light-emitting device suitable for wet preparation, which is provided with a hole blocking layer between an electron transport layer and a light-emitting layer.

Description

Platinum complex-based organic light-emitting device suitable for wet preparation

Technical Field

The invention relates to the field of organic electroluminescent devices, in particular to an organic light-emitting device based on a platinum complex and suitable for wet preparation.

Background

In the eighties of the last century, c.w.tang disclosed double-layer structured OLEDs (organic light emitting diodes) (US 4356429; appl.phys.lett.1987, 51, 12, 913). This discovery is based on the use of a multilayer structure comprising a light-emitting electron-transporting layer (emissive electron-transporting layer) and a hole-transporting layer of a suitable organic material. Selection of Alq₃(q: deprotonated 8-hydroxysilane group) as a luminescent electron transport material.

Although platinum is better than iridium in natural abundance and cost, only iridium (III) emitters are currently used in OLED display panels. This is because there are a number of technical problems that must be addressed before the platinum (II) emitter can be used in OLED display panel fabrication. Efficiency roll-off is one of the most serious problems encountered with platinum (II) emitters.

There remains a need in the art for high efficiency and low efficiency roll-off OLED devices containing pt (ii) complexes.

Disclosure of Invention

The present inventors have addressed the deficiencies of the prior art by providing a wet process for the preparation of an OLED with high efficiency and low roll-off efficiency by solution processing, resulting in an OLED characterized by a hole blocking layer between the electron transport layer and the light emitting layer. The wet preparation method provided by the invention promotes the practical application of the Pt (II) complex in the field of OLED.

In view of the above, the present inventors have adopted the following technical means to solve the above problems:

1. 4 Pt (II) complexes with high photoluminescence quantum efficiency (PLQY) were selected as luminescent materials: tetra-Pt-N, tetra-Pt-S1, tetra-Pt-S2, and tetra-Pt-S3;

2. 3 ambipolar organic materials were selected as host materials in OLEDs: m-TPAPy, o-TPAPy and o-CzPy;

3. careful spin coating and selection of organic solvents to coat the light emitting layer of the OLED with high quality;

4. then optimizing the thickness of each layer of the OLED, the improvement can be 1000cd/m²Maximum efficiency and efficiency roll-off at actual brightness.

Drawings

In order to more clearly illustrate the technical solution of the present invention, the present invention will be described in detail with reference to the accompanying drawings. It is to be expressly understood that the drawings are only illustrative of some specific embodiments of the invention and are not intended as a definition of the limits of the invention.

Fig. 1 is a schematic structural view of a representative OLED device of the present invention, which comprises, from bottom to top, a transparent substrate, an anode (ITO layer), a hole transport layer (PEDOT: PSS layer) (layer 1), a light emitting layer (EML) (layer 2) containing a host material and a light emitting pt (ii) complex, a Hole Blocking Layer (HBL) (layer 3) containing TmPyPb, an electron transport layer (layer 4) containing TPBi, an electron injection layer (layer 5) containing LiF, and a cathode (layer 6) made of Al;

FIG. 2 is a normalized EL spectrum of four tetradentate Pt (II) complexes in different host materials.

FIG. 3 shows the EQE-luminescence characteristics of tetra-Pt-N, tetra-Pt-S1, tetra-Pt-S2, and tetra-Pt-S3 in different host materials.

FIG. 4 is a reference CIE color coordinate system of an OLED device of the present invention.

FIG. 5 is a PLQY value for Pt (II) complexes dispersed in different hosts at a fixed concentration of 12 wt%.

Detailed description of the preferred embodiments

The following are embodiments of the preparation, physical properties and electroluminescence data of the platinum complex-based OLED devices as described in the present invention. The embodiments are presented to aid in understanding the invention and are not intended to, and should not be construed to, limit in any way the invention set forth in the claims appended hereto.

Unless otherwise indicated in the following examples and elsewhere in the specification and claims, all parts and percentages are by weight, all temperatures are in degrees Celsius and pressures are at or near atmospheric pressure.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, but in the event of conflict, the definitions set forth herein shall control.

As used in the specification and in the claims, the singular form of "a", "an", and "the" include plural referents unless the context clearly dictates otherwise.

All numbers or expressions referring to quantities of ingredients, process conditions, etc. used in the specification and claims are to be understood as modified in all instances by the term "about". The term "about" when referring to a quantity or a numerical range means that the quantity or numerical range referred to is an approximation within experimental variability (or within statistical experimental error), and thus the quantity or numerical range may vary between, for example, +5 of the quantity or numerical range.

All ranges directed to the same component or property are inclusive of the endpoints, and independently combinable. Because these ranges are continuous, they include every value between the minimum and maximum values. It should also be understood that any numerical range recited herein is intended to include all sub-ranges within that range.

When the present invention is directed to a physical property, such as molecular weight, or to a range of chemical properties, all combinations and subcombinations of ranges and specific embodiments therein are intended to be included. The term "comprising" (and related terms such as "comprising" or "including" or "having" or "including") includes embodiments that are, for example, any combination of materials, compositions, methods, or processes that "consist of or" consist essentially of the recited features.

As used in this specification and claims, "and/or" should be understood to mean "either or both" of the associated components, i.e., the components may be present in combination in some instances and separately in other instances. A plurality of components listed with "and/or" should be understood in the same way, i.e., "one or more" of the associated component. In addition to the "and/or" clause-specific components, other components may optionally be present, whether related or unrelated to those specifically identified components. Thus, as a non-limiting example, reference to "a and/or B," when used in conjunction with open ended words such as "comprising," may refer in one embodiment to a alone (optionally including components other than B); in another embodiment, reference may be made to B alone (optionally including components other than a); in yet another embodiment, refers to a and B (optionally including other components), and the like.

As used in this specification and the claims, the term "or" should be understood to have the same meaning as "and/or" as defined above. For example, when items are separated in a list, "or" and/or "should be interpreted as being inclusive, i.e., including at least one of more or components of the list, but also including more than one, and optionally other unlisted items. Only terms specifically directed to an opposite face such as "only one" or "exactly one," or "consisting of …" as used in the claims, shall mean including exactly one of the plurality or list of components. In general, the term "or" as used herein is considered to refer to an exclusive choice (i.e., one or the other but not both) only when there is an exclusive antecedent such as "or" one, "" only one, "or" exactly one.

It is to be understood that, unless explicitly indicated to the contrary, in any methods claimed herein that include more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited.

In the present invention, the inventors provide a wet process for the preparation of a high efficiency and low efficiency roll-off solution-processed OLED using a phosphorescent and luminescent tetradentate pt (ii) complex emitter and a bipolar organic host.

By comparing the performance of solution-treated Pt-OLEDs with various combinations of four tetradentate Pt (ii) complex emitters, including the following, in particular tetra-Pt-S2 and tetra-Pt-S3, and three bipolar organic hosts, we provide a method for the wet preparation of a high-efficiency and low-efficiency roll-off solution-treated OLED:

wherein the three ambipolar organic hosts comprise the following:

of the tetradentate Pt (ii) complexes studied, tetra-Pt-S3 exhibited the strongest electroluminescent properties due to its macromolecular backbone structure, high emission quantum efficiency, and excellent solubility in conventional organic solvents.

Solution processed OLEDs with tetra-Pt-S3 and m-TPAPy host material with a doping concentration of 4 wt% achieved high External Quantum Efficiencies (EQE) as high as 22.4%. At 1000cd m^-2At a high brightness of (1), thisThe EQE of the device only drops slightly to 21.0%.

OLED device

As shown in FIG. 1, the OLED device structure of the present invention is shown, which comprises a transparent substrate/ITO/PEDOT, PSS/Pt emitter, host material/TmPyPb/TPBi/LiF/Al, and the transparent substrate, ITO, layer 1, layer 2, layer 3, layer 4, layer 5 and layer 6 are shown in the figure. A transparent substrate, an anode (ITO layer), a hole transport layer (PEDOT: PSS layer) (layer 1), a light emitting layer (EML) (layer 2) containing a host material and a light emitting pt (ii) complex, a Hole Blocking Layer (HBL) (layer 3) containing TmPyPb, an electron transport layer (layer 4) containing TPBi, an electron injection layer (layer 5) containing LiF, and a cathode (layer 6) made of Al.

Specifically, glass is used as a transparent substrate, and then ITO is coated on the substrate to serve as an anode. Layer 1 is PEDOT: PSS, spin coated on an ITO substrate and dried in an oven for about 20 minutes. Layer 2 is a light emitting layer (EML) consisting of a host material and a light emitting pt (ii) complex, spin coated on layer 1, and then dried in a glove box on a hot plate at 50-150 ℃ for 5-30 minutes. Layer 3 is a Hole Blocking Layer (HBL) with TmPyPb. Layer 4 is an electron transport layer, and TPBi is selected. Layer 5 is an electron injection layer, selected from LiF. Layer 6 is the cathode, and is selected from Al. When the cathode and anode are connected to a dc power source and the applied voltage is higher than the turn-on voltage, the OLED device starts to operate and emits light.

The invention relates to the following specific technical scheme:

scheme 1. an OLED based on platinum complexes, characterized in that: a hole blocking layer is provided between the electron transport layer and the light emitting layer.

Scheme 2. the platinum complex-based OLED of scheme 1, wherein the hole blocking layer is TmPyPb; preferably, the thickness is 5-20nm, preferably 10 nm.

Scheme 3. the platinum complex-based OLED of scheme 1 or 2, which sequentially includes an anode ITO, a hole transport layer, a light emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a cathode.

Scheme 4. the platinum complex-based OLED of scheme 3, wherein the light-emitting layer is composed of a blend of a host material and a pt (ii) complex.

Scheme 5. the platinum complex-based OLED of scheme 4, wherein the host material is selected from the group consisting of m-TPAPy, o-TPAPy and o-CzPy.

Scheme 6. the platinum complex-based OLED of any one of schemes 4 to 5, wherein the mass percentage of the host material in the light-emitting layer is 80 to 96 wt%; preferably, the mass percentage of the luminescent material is 96 wt%.

Scheme 7. the platinum complex-based OLED according to any one of schemes 4 to 6, wherein the Pt (ii) complex is selected from the group consisting of tetra-Pt-N, tetra-Pt-S1, tetra-Pt-S2 and tetra-Pt-S3; preferably, the Pt (II) complex is selected from tetra-Pt-N and tetra-Pt-S3; preferably, the Pt (II) complex is tetra-Pt-S3.

Scheme 8. the platinum complex-based OLED of any one of schemes 4 to 7, wherein the mass percentage of the light emitting material in the light emitting layer is 4 to 20 wt%; preferably, the mass percentage of the luminescent material is 4 wt%.

Scheme 9. the platinum complex-based OLED according to any one of schemes 4 to 8, wherein the thickness of the light-emitting layer is 10 to 100 nm; preferably, the thickness of the light emitting layer is 60 nm.

Scheme 10. the platinum complex-based OLED according to any one of schemes 3 to 9, wherein the electron transport layer is TPBi; preferably, it has a thickness of 30-80nm, preferably 40 nm.

Scheme 11. the platinum complex-based OLED according to any one of schemes 3 to 10, wherein the electron injection layer is LiF; preferably, the thickness is 0.5-5nm, preferably 1.2 nm.

Scheme 12. the platinum complex-based OLED according to any one of schemes 3 to 11, wherein the cathode is Al; preferably, it has a thickness of 30-200nm, preferably 150 nm.

Scheme 13. the platinum complex-based OLED according to any one of schemes 3 to 12, wherein the hole transport layer is PEDOT: PSS.

Scheme 14. the platinum complex-based OLED of any one of schemes 3 to 13, wherein the anode ITO is an ITO-coated substrate.

Scheme 15. the platinum complex-based OLED of scheme 14, wherein the substrate is electrically insulating and optically transparent; preferably, the substrate comprises glass, plastic foil or other suitable material; preferably, the anode ITO is an ITO-coated glass substrate.

Scheme 16. the platinum complex-based OLED of scheme 14, wherein the substrate is electrically insulating and optically opaque; preferably, the substrate comprises one or more semiconductor materials or ceramics.

Scheme 17. a method of making an OLED comprising the steps of:

1) spin coating the hole transport layer on the substrate and drying;

2) spin coating a light emitting layer on the hole transport layer;

3) annealing the device obtained in the step 2), and then transferring the device to a vacuum deposition system to avoid air contact; and

4) a hole blocking layer, an electron transport layer, an electron injection layer and a cathode are sequentially deposited by thermal evaporation.

Scheme 18. the preparation method of scheme 17, wherein in step 2) the light emitting layer is composed of a blend of a host material and a pt (ii) complex.

Scheme 19. the preparation process of scheme 18 wherein in step 2) the host material is selected from the group consisting of m-TPAPy, o-TPAPy and o-CzPy.

Scheme 20. the preparation process of any one of schemes 18 to 19, wherein the concentration of the host material in step 2) is 5 to 20 wt%; preferably, the concentration of the host material is 10 wt%.

Scheme 21. the preparation process according to any one of schemes 18 to 20, wherein the Pt (ii) complex in step 2) is selected from tetra-Pt-N, tetra-Pt-S1, tetra-Pt-S2 and tetra-Pt-S3; preferably, the Pt (II) complex is selected from tetra-Pt-S2 and tetra-Pt-S3; preferably, the Pt (II) complex is tetra-Pt-S3.

Scheme 22. the preparation process of any one of schemes 18 to 21, wherein the concentration of the pt (ii) complex in step 2) is 0.5 to 5 wt%; preferably, the concentration of the Pt (II) complex is 2 wt%.

Scheme 23. the production method of any one of schemes 17 to 22, wherein the thickness of the light emitting layer in step 2) is 10 to 100 nm; preferably, the thickness of the light emitting layer is 60 nm.

Scheme 24. the preparation process of any of schemes 17 to 23, wherein the spin coating in step 2) is on N₂The filled glove box was filled with chlorobenzene.

Scheme 25. the preparation process of any one of schemes 17 to 24, wherein the hole blocking layer in step 4) is TmPyPb; preferably, it has a thickness of 5-20 nm; preferably 10 nm.

Scheme 26. the preparation method of any one of schemes 17 to 25, wherein the electron transport layer in step 4) is TPBi; preferably, it has a thickness of 30-80 nm; preferably 40 nm.

Scheme 27. the preparation process of any one of schemes 17 to 26, wherein the electron injection layer in step 4) is LiF; preferably, the thickness thereof is 0.5 to 5 nm; preferably 1.2 nm.

Scheme 28. the preparation process according to any one of schemes 17 to 27, wherein the cathode in step 4) is Al; preferably, the thickness is 30-200 nm; preferably 150 nm.

Scheme 29. the method of manufacture of any of schemes 17-28, wherein the thermal evaporation in step 4) is at most about 10^- ⁸At a pressure of mbar.

Scheme 30. the method of any one of schemes 17 to 29, wherein the deposition rate of the organic material in step 4) is 0.01 to 0.2nm/s, and during the deposition, the substrate is rotated to promote uniformity of each layer.

Scheme 31. the preparation method of any one of schemes 17 to 30, wherein the deposition rate of LiF in step 4) is 0.005 to 0.03 nm/s.

Scheme 32. the preparation process of any one of schemes 17 to 31, wherein the deposition rate of Al in step 4) is 0.05 to 0.2 nm/s.

Scheme 33. the preparation process of any one of schemes 17 to 32, wherein the drying in step 3) is performed in a glove box at about 60 to 120 ℃, preferably about 70 ℃; preferably, the annealing is performed for about 60 minutes.

Scheme 34 the preparation process of any one of schemes 17 to 33, wherein the hole transport layer in step 1) is PEDOT: PSS.

Scheme 35. the method of making of any of schemes 17-34, wherein the substrate in step 1) is an ITO-coated glass substrate.

Scheme 36. the method of any one of schemes 17-35, wherein the drying in step 1) is baked at about 120 ℃ for about 20 minutes to remove residual aqueous solvent.

Scheme 37. the method of manufacturing of any one of schemes 17 to 36, wherein the substrate is cleaned prior to step 1); preferably, the cleaning is performed by rinsing in an ultrasonic bath of Decon90 detergent and deionized water.

Scheme 38. the preparation process of scheme 37, wherein after the above cleaning the substrate is cleaned in a continuous ultrasonic bath of deionized water, acetone and isopropanol.

Scheme 39. the preparation of scheme 38 wherein after cleaning is complete it is dried in an oven for about 1 hour.

Scheme 40. the preparation process according to any one of schemes 17 to 39, wherein the purity is adjusted after step 4)>99% of N₂The gas is charged into the chamber of the deposition system until the pressure of the chamber is above 50 kPa.

Scheme 41. an OLED based on a platinum complex prepared by the method of any one of schemes 17-41.

In a particular embodiment, the host material includes, but is not limited to, one or more of the following:

in another embodiment, the luminescent material is a tetradentate pt (ii) complex, including but not limited to one or more of the following:

examples

For the purposes of clarity and ease of understanding of the present invention, embodiments of the present invention are first provided that relate to the Chinese comparison of English shorthand, as follows:

al: aluminium

ITO: indium tin oxide

LiF: lithium fluoride

PEDOT PSS: poly (3, 4-ethylenedioxythiophene) ((styrenesulfonic acid))

TmPyPb: 3,3'- [5' - [3- (3-pyridyl) phenyl ] [1,1':3',1 '-terphenyl ] -3, 3' -diyl ] bipyridine

TPBi: 1,3, 5-tris (1-phenyl-1H-benzimidazol-2-yl) benzene

Example 1: wet preparation of OLEDs

Materials: the luminescent material is synthesized by the inventor according to the known method; PEDOT, PSS from Heraeus; LiF was purchased from sigma-Aldrich; m-TPAPy, o-TPAPy and o-CZPy, as well as other transport materials, were purchased from Luminessence technology Corp; organic solvents for dissolving organic materials were obtained from the chemical institute of hong kong university. All materials were used as received.

Cleaning a substrate: glass slides with pre-patterned ITO electrodes used as substrates for OLEDs were cleaned in an ultrasonic bath of Decon90 detergent and deionized water, rinsed with deionized water. It was then cleaned in a continuous ultrasonic bath of deionized water, acetone and isopropanol, followed by drying in an oven for 1 hour.

Fabrication and characterization of the devices: PEDOT: PSS was spin coated on a clean ITO coated glass substrate in a clean room and baked at 120 ℃ for 20 minutes to remove residual aqueous solvent. Preparing a main material and a Pt (II) complex with chlorobenzene into solutions respectively, wherein the concentration of the main material is 5-20mg/ml, and the concentration of the Pt (II) complex is 0.5-5 mg/ml. And then mixing a certain amount of preparation solution containing the main material and the Pt (II) complex to ensure that the mass ratio of the main material to the Pt complex is 96: 4-80: 20, and spin-coating the prepared mixed solution on a PEDOT (polymer substrate) PSS (polymer substrate) layer by using chlorobenzene in a glove box filled with N2. All EMLs were 10-100nm thick. All devices were then annealed at 70 ℃ for 60 minutes in a glove box and then transferred to a Kurt j. Finally, at 10^-8TmPyPb (10nm), TPBi (40nm), LiF (1.2nm) and Al (150nm) were deposited in succession by thermal evaporation at a pressure of mbar.

The deposition rate of the organic material is 0.01-0.2nm/s, during which the substrate is rotated to promote uniformity of each layer. The deposition rate of LiF is 0.005-0.03nm/s, the deposition rate of Al is 0.05-0.2nm/s, and the substrate cannot rotate during the deposition process.

After the deposition is completed, the purity is measured>99% of N₂The gas was charged into the chamber of the OLED deposition system until the pressure of the chamber was above 50kPa, then the chamber door was opened and the device was removed.

In this example, the host material used has the following structural formula:

the Pt (II) complex has the following structural formula:

example 2: performance testing of OLEDs

The method comprises the following steps: the EL spectrum, luminescence and CIE coordinates were measured by Photo Research Inc PR-655. The voltage-current characteristics were measured using a Keithley 2400 source meter measurement unit. The EQE and power efficiency are calculated by assuming a Lambertian distribution.

As a result: a maximum EQE of 22.4% was achieved at a doping concentration of the lowest 4 wt%, at 1000cd m^-2The EQE of this device decreased slightly to 21.0% at high brightness. These values are comparable to, and even higher than, solution-treated OLEDs based on phosphorescent ir (iii) and TADF emitters.

Specifically as shown in FIG. 2, FIG. 2 depicts the normalized EL spectra of OLEDs based on a) tetra-Pt-N, b) tetra-Pt-S1, c) tetra-Pt-S2, and d) tetra-Pt-S3 in different host materials (m-TPAPy, o-TPAPy, and o-CzPy), with the doping concentration fixed at 12 wt%.

It is noteworthy that the EL spectrum of the tetra-Pt-S1 depends on the host, and that the maximum emission of the tetra-Pt-S1 device is slightly red-shifted from 511nm to 514nm and then 517nm when the host is m-TPAPy, o-TPAPy and o-CzPy, respectively.

From the above experimental results, it can be obtained that tetra-Pt-S3 shows the best electroluminescent property among tetradentate Pt (ii) complexes due to its bulky molecular scaffold structure, high emission quantum yield and good solubility in common organic solvents.

FIG. 3 is a graph depicting EQE-luminescence characteristics of devices based on a) tetra-Pt-N, b) tetra-Pt-S1, c) tetra-Pt-S2, and d) tetra-Pt-S3 in different host materials.

The key parameters for these devices are listed in tables 1 and 2 below. At a minimum concentration of 4 wt%, a maximum EQE of 22.4% is achieved, and at high brightness of 1000cd m^-2When the temperature is high, the EQE is slightly reduced to 21.0 percent. These values are comparable to, and even higher than, solution-treated OLEDs based on phosphorescent ir (iii) and TADF emitters.

TABLE 1 Key EL Performance data for tetra-Pt-N, tetra-Pt-S1, tetra-Pt-S2, and tetra-Pt-S3

TABLE 2 OLEDs device Performance of m-TPAPy doped tetra-Pt-S3

In the above table, L_maxCE is current efficiency, PE is power efficiency, EQE is external quantum efficiency, and CIE coordinates are color coordinates of the commission internationale de l' eclairage.

Fig. 4 is the CIE color coordinates showing yellow to green colors, indicating that high efficiency and low efficiency roll-off OLEDs can be obtained by solution processing, which is an inexpensive and industrially suitable process.

FIG. 5 depicts PLQY of tetra-Pt-N, tetra-Pt-S1, tetra-Pt-S2, and tetra-Pt-S3 dispersed in m-TPAPy, o-TPAPy, and o-CzPy thin films, respectively, with the doping concentration fixed at 12 wt%. Similar to that observed in solution, PLQY for tetra-Pt-S2 was lower than that of the other complexes. High PLQY of 0.83 and 0.81 was achieved in m-TPAPy films with tetra-Pt-N and tetra-Pt-S3 dopants, respectively.

On the other hand, in m-TPAPBulk emission was observed in the tetra-Pt-S1 and tetra-Pt-S2 samples in y, resulting in relatively low PLQY for these samples (0.62 for tetra-Pt-S1 and 0.22 for tetra-Pt-S2). Such host emission may be the result of reverse energy transfer, as a result of E of tetra-Pt-S1(2.49eV) and tetra-Pt-S2(2.51eV)_tRelatively high and/or insufficient energy transfer of m-TPAPy (Et 2.61eV) to the emitter. By using o-CzPy (Et ═ 2.70eV) instead of m-TPAPy, the bulk emission disappeared in both samples of tetra-Pt-S1 and tetra-Pt-S2, so their PLQY increased to 0.71 and 0.46, respectively.

Claims

1. An OLED based on a platinum complex, characterized in that: a hole blocking layer is arranged between the electron transport layer and the light-emitting layer; preferably, the hole blocking layer is TmPyPb, preferably 10nm thick.

2. The platinum complex-based OLED of claim 1, which comprises an anode ITO, a hole transport layer, a light emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer and a cathode, in that order.

3. The platinum complex-based OLED of claim 2 wherein the light-emitting layer is comprised of a blend of a host material and a pt (ii) complex; preferably, the host material is selected from m-TPAPy, o-TPAPy and o-CzPy, preferably, the Pt (II) complex is selected from tetra-Pt-N, tetra-Pt-S1, tetra-Pt-S2 and tetra-Pt-S3, preferably, the mass percentage of the Pt (II) complex in the light-emitting layer is 4 wt% to 20 wt%; preferably, the thickness of the light emitting layer is 10 to 100 nm.

4. The platinum complex-based OLED according to any one of claims 2 to 3, wherein the electron transport layer is TPBi, preferably having a thickness of 40 nm; preferably, wherein the electron injection layer is LiF, preferably, 1.2nm in thickness; preferably, wherein the cathode is Al, preferably it has a thickness of 150 nm.

5. The platinum complex-based OLED according to any one of claims 2 to 4, wherein the hole transport layer is PEDOT PSS; preferably, wherein the anode ITO is an ITO-coated substrate; preferably, wherein the anode ITO is an ITO-coated glass substrate.